Fluorescent Photopatterns from Thin Films and Aqueous Polymer Dots Composed of Aminated Polydimethylsiloxane and a Conjugated Polymer

The microscale patterning of luminescent and other functional materials is important for optoelectronics, sensor arrays, anticounterfeiting, and many other technologies and applications. Photopatterning is a well-established and advantageous approach, for which multicomponent resins are the norm. Here, we demonstrate photopatterning that is greatly simplified in its method and in its formulation. The only two components are an aminated polydimethylsiloxane and a semiconducting polymer, where the latter has the dual role of imparting fluorescence to the photopatterns and sensitizing singlet oxygen to drive imine bond formation and cross-linking between chains of aminated polydimethylsiloxane. Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT) was used in tandem with aminopropylmethylsiloxane-dimethylsiloxane copolymer (PDMS-NH₂) for most experiments; however, multiple conjugated semiconducting polymers showed potential to be utilized with this method. Fluorescent patterns with fidelity and resolution on the order of tens of microns were prepared from spin-coated thin films of the two polymers, as well as from aqueous solutions of nanoscale polymer dots (Pdots) prepared from the two polymers. The aqueous Pdot method had superior pattern fidelity to the thin-film method and more homogeneous fluorescence at the microscale. Characterization of the mechanism of on-substrate photopatterning via aqueous Pdots revealed cross-linking between individual Pdots to grow larger discrete particles and to form networks between these enlarged particles. This simple, resin-free approach stands to reduce cost and waste, facilitate waste management, and eliminate potential fluorescence quenching effects associated with multicomponent photopatterning resin formulations.